Enantioselective and diastereoselective control in the synthesis of pharmacophores is now mandated due to the diversity of physiological properties exhibited by stereoisomers. Although olefin metathesis chemistry has undergone a renaissance in the development of ruthenium alkylidene catalysts, general stereochemical control remains a challenge. This proposal outlines the development of a new family of readily accessible, enantioselective ruthenium metathesis catalysts, based on amino acid chirality. These catalysts will be used to effect asymmetric ring closing metathesis (ARCM) to form unsaturated heterocyclic amines, important building blocks in the preparation of natural products. To illustrate this methodology, an enantioselective route for the rapid assembly of all four diastereomers of the antibiotic agent (-)-sedamine is proposed. Additionally, the effect of the chiral metal center in this new class of metathesis catalysts will be explored in controlling E/Z diastereocontrol in olefin cross-metathesis, an important application of metathesis in natural product synthesis. [unreadable] [unreadable]